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Charge was calculated by size of receiver height and diameter. and mounting direction ( vertical or horizontal) We all have books and literature from united refrigeration and refrigeration research. That will give you the capacity of it. That is how our company and a few of the 20 plus year guys have always said to do it.
At my previous company I was always told to charge to a til glass.

I have been hesitant lately of over charging I had one case over the summer that I over charged by about 6lbs and got a call back on the WIF not holding temp. But that was charging til a clear glass and it bit me.

So now Ive been trying to use as literature as possible when charging. I also do agree with you guys that once ok but multiple times odds are that it is more than likely not a equipment issue. But everything was installed and charged to the letter so that is the part that makes it odd. and when a new headmaster is installed everything acts properly.

Yes, Lennox owns Heatcraft. One brand that wasn't mentioned was Kysor/Warren, also under Heatcraft. Rumor has it that Lennox will roll out a Heatcraft Service soon, specializing in anything Com. Ref. What do you guys think? Was not the Service Experts and National Accounts Services businesses enough?!

As you can see from this, 2-3 pounds is about it for even their larger units.

Thats what heatcraft said when I called a while back. I was installing a new condensing unit but there was nothing in the manual on how to calculate the charge for the headmaster on the microchannel coils. He said there is two ways, clear the glass and add 3 pounds, or charge to 90% receiver capacity.

Thats what heatcraft said when I called a while back. I was installing a new condensing unit but there was nothing in the manual on how to calculate the charge for the headmaster on the microchannel coils. He said there is two ways, clear the glass and add 3 pounds, or charge to 90% receiver capacity.

90% receiver is what I have used and never missed. Well so far anyway.

Weigh in charge until glass is full. Take that weight and figure out what 10% of that is and weigh that in. Heatcraft tech support told me that 12 years ago and I have done it ever since with out fail.

Weigh in charge until glass is full. Take that weight and figure out what 10% of that is and weigh that in. Heatcraft tech support told me that 12 years ago and I have done it ever since with out fail.

Re: Charging Heatcraft Condensing Units

Heatcraft's I & O manuals for their condensing units leave a lot to be desired regarding how to properly charge a system. In addition, their units' data tags don't indicate anything about either receiver capacity or winter charge requirement with a condenser flooding control like some other manufacturers do.

Just as I had to do some digging to find that PDF on the HyperCore flooding charge info, it took a bit of searching all of their published literature to find any mention of winter charging methods.

Here's a little ditty from a FAQ page which actually discusses it...in part (Scroll down to near the bottom under "Disadvantages":

It states that after the sightglass is cleared add 15% of the initial weighed-in charge for operation down to 0ºF or an additional 30% for -20ºF.

Bear in mind that these guidelines were written before the advent of the microchannel designs and their vastly reduced coil volumes.

A more correct method for HyperCore units would be to clear the SG (while maintaining a condensing temperature above 105ºF by blocking airflow as necessary) and add the 2-3 lbs flooding charge as indicated in my previous link.